Q $3)$ The horizontal rigid beam ABCD is

supported by vertical bars BE and CF and is

loaded by vertical forces $P_1=400kN$ and $P_2=$

$360$ kN acting at points A and D $,$ respectively

$($see figure$).$ Bars BE and CF are made of steel

$(E=200$GPa$)$ and have cross$-$sectional areas

$A_{BE}=11,100m{m}^2$ and $A_{CF}=9,280m{m}^2.$ The

distances between various points on the bars are

shown in the figure.

Determine the vertical displacements ${}_A$ and ${}_D$

of points A and $D,$ respectively.